Heat gun defroster



Oct. 12, 1965 J. 5. GRAVES 3,211,890

HEAT GUN DEFROSTER Original Filed June 27, 1963 INVENTOR JOEL S. GRAVESUnited States Patent 1 Claim. '(Cl. 219370) This application is adivision of application Serial No. 291,014, filed June 27, 1963, forHeat Gun Defroster.

The present invention relates to defrosters and more particularly toportable, electric, forced hot air defrosters for defrosting theWindshields of motor vehicles.

An object of the invention is to provide an improved portable electrichot air defroster.

Another object of the invention is to provide improved means for heatinga current of air within a forced hot air defroster.

Broadly, the present invention includes a gun-shaped case of plastic orsimilar material having an air intake port and an air outlet porttherein, a small rotary fan arranged to force outwardly through said airoutlet port air drawn inwardly through said intake port, a smallelectric motor arranged to rotate said fan, an electric resistanceelement arranged to heat said outwardly directed air, a plug adapted forconnection with the electrical system of a motor vehicle by insertion inthe cigar lighter socket, and electric wiring operativelyinterconnecting said plug with said motor and heater element to energizesame. An insulated heat chamber is provided surrounding said resistanceelement and through which the flow of outwardly directed air isconstrained to pass. The unique configuration of the heat chamber issuch as to impart to the outwardly directed air an unusually hightemperature while increasing the efficiency of the device, reducing theamount of current required, eliminating the overloading of the vehicleselectric circuit, and lengthening the life of the resistance element.

The above and other objects of the invention which will later becomeapparent as the following description proceeds, are attained by thepresent invention, a preferred embodiment of which has been illustratedby way of example only, in the accompanying drawing, forming a part ofthis specification in which like characters are employed to designatelike parts throughout the same, and wherein:

FIGURE 1 is a side sectional view of a heat gun defroster.

FIGURE 2 is a view taken along line 22 of FIG- URE 1.

FIGURE 3 is a view of a heat gun defroster in operation.

Referring now more particularly to the drawing, 1 provide a gun-shapedcase preferably formed of two symmetrical sections of plastic or otherinexpensive, durable, light-Weight material, mutually engaged byconventional means, such as screws or the like inserted transverselythrough one section and threadably engaged within threaded sockets 12extending from the inner surface of the other section. A generallycircular air inlet port 13 is formed in the top of case 10 near the rearthereof, and an air outlet port 14 is formed at the forward or muzzleend of the case. A squirrel case type rotary fan 17 is operativelymounted upon the shaft of a small electric motor 18 within the receiverportion of case 10, and the motor, in turn, is mounted within the handleportion of the case by any convenient mounting means such as a screwextending through the sidewall of the handle portion of the case andthreadably engaged within a threaded aperture 20 in the outer wall ofthe motor. Fan 17 is thus supported below air inlet port 13. A flange 24surrounding the upper end of a sleeve 22 is supported within a circularchannel 26 surrounding the inside of air inlet port 13, so that thelower end of the sleeve extends downwardly to a point slightly above fan17.

I provide an insulated heat chamber 28 in the form of a hollow,truncated, metal cone 30 mounted within the barrel portion of case 10 bya bolt 32 or the like extending transversely through the case and cone.Cone 30 is formed of a metal, such as preferably aluminum, adapted toreflect heat inwardly from its inner surface. The sides of cone 30converge toward the forward end of case 10, and the smaller end of thecone forms an orifice 34 opening upon air exhaust port 14. A flat,generally trapezoidal piece of asbestos 36 is wedged within cone 30 fromthe rear or larger end thereof. A heating element 38, consisting of anelectrical resistance wire, is folded rearwardly about the forward endof asbestos piece 36 and is thereby retained from slipping rearwardly.The rear ends of heating element 38 are also crossed about the rear endof asbestos piece 36, shown generally at 39, for a purpose moreparticularly hereinafter described.

An electrical plug 40 adapted to be operatively receive-d within theconventional cigar lighter socket of a motor vehicle 42 transmitselectrical energy from the electrical system of the vehicle to energizemotor 18 and heater element 38 through electrical wires 44.

In operation, when plug 40 is inserted into the cigar lighter socket ofmotor vehicle 42, electrical current is transmitted through wires 44 andenergizes both electrical motor 18 and heater element 38, causing fan 17to rotate and the heater element to radiate heat within cone 30. Themotion of fan 17 forces air forwardly and outwardly from case 10 throughcone 30, orifice 34, and air outlet port 14. As such air passes throughcone 30, it is heated by contact with heater element 38 and by heatenergy radiated from said element.

The handle portion of the device is gripped manually by the operator andthe barrel portion aimed in a natural manner toward the windshield orother pane of glass from which frost or ice is sought to be removed. Thelength of the cord is sufficient so that not only the inner surface ofsuch pane of glass may be thus defrosted but also the operator may passthe device through an open window or door of the vehicle and employ thedevice outside of the car, as illustrated in FIGURE 3, while plug 40 isstill engaged within the cigar lighter socket of the vehicle.

Particular attention is invited to the configuration and nature of heatchamber 28 formed by aluminum cone 30. The constant slope of the sidesof cone 30 minimizes turbulence of air entering the heat chamber formedthereby. Further, when the rear ends of heating element 38 are crossedabout the rear end of asbestos piece 36, as shown at 39, so that thefolded ends of the element are parallel to the longitudinal axis of cone30, the constant slope of the sides of the cone cause an increase in thevelocity of air passing forwardly through the cone generallyproportionate to the proximity of the molecules of such air to theportion of the heating element to which they are exposed, causing themolecules to be exposed to heat from the heating element for timeintervals which are inversely proportional to the heat energy absorbedthereby. Air entering cone 30 is thus heated uniformly as it passesforwardly therethrough.

It should also be particularly noted that the slope of the sides of cone30 forms a dead air space 46, the crosssectional area of which increasesdirectly with the decrease in cross-sectional area of cone 30 throughoutthe length of heating element 38. The insulating effect of dead airspace 46 against heat loss through the wall of cone 30 thus increases asthe temperature of air passing through the cone increases during itspassage therethrough.

I have found that where no heat chamber 28 is provided, fifteen toeighteen amperes of electrical current is required to produce at airexhaust port 14 air having a temperature of from 150 degrees Fahrenheitto 175 degrees Fahrenheit, and such flow of current frequently causesthe fuses of the electrical system of the motor vehicle to be blown.When heat chamber 28 is employed, however, I have found that onlyapproximately eight and one-half amperes of electrical current isrequired to product at air exhaust port 14 air having a temperature ofapproximately 200 degrees Fahrenheit. Heat chamber 28 thus increases theair temperature at outlet port 14 by 12.5% to 25%, but, even moreimportantly, does so with a current drain of only 47% to 57% of thatrequired where the heat chamber is not used. Thus not only theeifectiveness of the device as a defroster is increased but theefiiciency thereof is dramatically increased with less drain on thesource of electrical energy, increased life for heater element 38, andthe avoidance of blown fuses.

It is to be understood that the form of the invention herewith shown anddescribed is to be taken as a preferred embodiment of the same and thatresort may be had to various changes in construction Without departingfrom the scope of the subjoined claim.

What is claimed is:

In combination, a gun-shaped case of molded plastic, said case having ahandle portion and a cylindrical barrel portion; said handle portionhaving an air inlet port; said barrel portion having an axis, a muzzleend, and an air outlet port at said muzzle end; a forwardly directedhollow truncated cone disposed within said barrel portion, said conehaving a large end and a small end and formed of material having highheat reflective characteristics, said cone having an axis and said axisof said cone aligned to coincide with said axis of said barrel portionof said case, said large end of said cone positioned adjacent saidhandle portion of said case and said small end of said cone positionedadjacent said air outlet port of said barrel portion of said case; anopen spiral coil electric resistance heating element positioned Withinsaid cone, said heating element having two ends, said ends being foldedadjacent said large end of said cone about an insulating supportingelement longitudinally aligned with said axis of said cone to form agenerally U-shaped heating element with the legs thereof maintainedsubstantially parallel to the common longitudinal axis of said cone andsaid barrel portion of said case, whereby air is permitted to flowthrough said legs of said open spiral coil heating element, an annulardead air space is formed by said cone and said barrel portion of saidcase, the transverse cross-sectional area of said dead air spaceincreasing directly with the decrease in cross-sectional area of saidcone throughout the length of said heating element from the large endtowards the small end of said cone, and said barrel portion of said caseis insulated from said heating element; an electric motor mounted withinsaid handle portion of said case; a fan operatively mounted upon saidmotor and arranged to force air forwardly through said cone andoutwardly through said outlet port; an electric plug adapted to beoperatively received within the cigar lighter socket of a motor vehicle;and means for transmitting electric current from said plug to said motorand said heating element to electrically energize same.

References Cited by the Examiner UNITED STATES PATENTS 981,641 1/11Halliwell 219-374 X 1,346,471 7/20 Slater 219-374 X 1,564,896 12/25Rinker et a1 219-375 X 1,738,164 12/29 Zingg 219-374 X 2,049,812 8/36Loacker 219-369 X 2,432,067 12/47 Morse 219-374 X 2,514,528 7/50 Wahl219-374 X 3,026,401 3/62 Cheviron 219-369 X RICHARD M. WOOD, PrimaryExaminer.

ANTHONY BARTIS, Examiner.

